This page provides technical resources for researchers interested in porous silicon and in silicon nanomaterials:

• Safety protocols for handling HF
• Instructional videos on preparation, processing, and safety concerns associated with porous silicon
• Engineering diagrams for equipment used in porous silicon research
• Software used to etch and to characterize porous silicon layers
• Companies, Institutes, Government, and Academic Labs who have programmatic interests in porous silicon or related forms of nanophase silicon
• Upcoming meetings of interest to the porous silicon community
• Educational modules associated with the UC San Diego MRSEC that involve porous silicon or related nanomaterials

Working with Hydrofluoric Acid

Hydrofluoric acid is a unique hazard associated with silicon nanomaterials. It is used to dissolve silicon dioxide (SiO₂) and it is a key ingredient in electrolytes used in the electrochemical and chemical etching procedures.
CAUTION: EXTREMELY HAZARDOUS LIQUID AND VAPOR. CAUSES SEVERE BURNS WHICH MAY NOT BE IMMEDIATELY PAINFUL OR VISIBLE. MAY BE FATAL IF SWALLOWED OR INHALED. LIQUID AND VAPOR CAN BURN SKIN, EYES AND RESPIRATORY TRACT. CAUSES BONE DAMAGE. In the vapor phase, hydrofluoric acid is more toxic than cyanide gas. When handling HF, you should wear a lab coat, a chemical apron, butyl rubber gloves, goggles, and a face shield. Proper attire and handling protocols are shown in the video “Etching 101“. A Safety Data Sheet, description of the hazard, and First Aid treatment for HF burns is posted here.

“Safety Tour” document

This is a document meant to onboard all members of the Sailor Lab. It describes the major hazards and safety procedures associated with working in the Silicon Nanomaterials lab at UC San Diego, including appropriate PPE, working with HF, cleaning up HF spills, and much more. You must request access to download this file.

“Etching 101” video: how to make porous silicon

Instructional video made by Gha Young Lee (in the 2015 SSSiN), on the preparation of porous silicon by electrochemial anodization of  crystalline silicon wafers in aqueous HF:ethanol electrolytes. Includes tips on cell design, mounting a wafer, leak-checking the cell, safety procedures, and personal protective equipment. The procedure is focused on the preparations given in “Porous Silicon in Practice: Preparation, Characterization, and Applications.” (Wiley-VCH: Weinheim, Germany, 2012).

“Schlenk Line Operation” video: how to set up an airless Schlenk line

Instructional YouTube video “Schlenk Line Operation” made by Roghiye Kazimi and James Fulmer (SSSiN 2019), on the setting up an taking down of a Schlenk line. A Schlenk line is a type of vacuum apparatus that allows the manipulation of air-sensitive compounds. Our group uses it to perform silicon surface modification chemistries such as the ring-opening of cyclic silanes and hydrosilylation, both of which need to be performed in the absence of oxygen and water.

Standard etch cell

PDF file of the top and the base of a Teflon electrochemical cell used for two-electrode anodization of silicon chips. This design incorporates screws that enter from the bottom of the cell. Makes a porous Si layer approximately 1.24 cm in diameter, with 1.2 cm² of exposed area.

Large etch cell

PDF file of the top and the base of a Teflon electrochemical cell used for two-electrode anodization of silicon chips. The most recent design, this incorporates screws that open from the bottom of the cell. Makes a porous Si layer approximately 3.5 cm in diameter, with 9.6 cm² of exposed area. Accommodates 2-inch wafers.

Glass top and valve

simple sketch of a glass fixture for sealing the Standard etch cell via an 18mm O-ring. Allows one to perform anaerobic electrochemistry, spectroscopy, or other manipulations of the sample under a controlled atmosphere. Once you etch, clean, and dry your sample, you can then add this top to the Standard etch cell without un-mounting your sample.

Clamp for glass top

an aluminum fixture to hold the above glass top in place in the Standard etch cell.

These programs are provided free of charge to the research community. The author does not warrant their accuracy or stability. Please report any bugs or problems to the author. Detailed descriptions of their use and application can be found in the book “Porous Silicon in Practice (M.J. Sailor, 2012),” available from Wiley-VCH.

Electrochemical Etching Programs

to prepare porous silicon nanoparticles, photonic crystals, and “quantum dot” nanostructures by controlled current (galvanostatic) anodization of silicon wafers.

CAUTION: Preparation of porous silicon uses electrolytes containing aqueous hydrofluoric acid (HF). HF is highly toxic and corrosive, and the user should be familiar with the proper use and handling of HF before attempting to perform procedures employing HF-containing electrolytes. All manipulations of HF should be performed with goggles, a face shield, a rubber chemical apron, and butyl rubber gloves that extend to the elbow.

Keithley2460_Etch_Program_v28, a vi (virtual instrument) for the National Instruments Labview program that drives a Keithley 2460 Sourcemeter (in current source mode). This is an all-digital interface that allows current-controlled anodization (etching of silicon to generate porous silicon) at a data rate of 10 points per second. These programs (contained in a .zip archive) are designed to connect a PC to the Sourcemeter, via either the VISA (ethernet) or USB interfaces. These are National Instruments LABVIEW virtual instrument and library files; you need the National Instruments LABVIEW program loaded on your computer to run them.
The .zip archive contains the following programs:

• (1) Keithley Sourcemeter 2460 setup notes, a Microsoft Word document that gives a bit of guidance on setup.
• (2) Keithley2460_Etch_Program_v28.vi, National Instruments LABVIEW virtual instrument file that drives the Keithley 2460 Sourcemeter.
• (3) Extract Numbers.vi, National Instruments LABVIEW virtual instrument file that is called by the vi in (2).
• (4) a bunch of .llb files (in the instr.lib folder) that are used by the above programs. You probably already have all these files in your National Instruments LABVIEW install.

WaveformDesigner6_3, an Igor Pro (www.wavemetrics.com) program used to design waveforms for input to the LABVIEW vi “Keithley2460_Etch_Program” listed above (August 17, 2024). Note the file will have a .pxp extension which is the “packed experiment” format used by Igor Pro in either Mac or PC versions. The program can generate single layers (“straight etch”), multilayers, rugate filters, Bragg stacks, and “perforated etch” profiles. “Save profile to disk…” will output a .txt file that is a single column of numbers, separated by <cr>, that is readable by the Keithley2460_Etch_Program.

Data Workup and Analysis Programs

Spectra_4_6 (.zip archive) Subroutines written for Igor Pro 9 (64-bit) (www.wavemetrics.com) designed to work up large numbers of (reflectivity or interference) spectra from Ocean Optics (“OceanView”) spectrometers but can load other .txt type files that have signal and wavelength in two separate columns. Improved file handling, capability to perform FFT on selected regions of a spectrum, monitoring of intensity and position of peak in the reflectivity spectrum or in the FFT, integrate between cursors, measure empirical half-life from decays. (Nov 5, 2024)

SLIM_27_6 (.zip archive) Subroutines written for Igor Pro 9 (64-bit) (www.wavemetrics.com) designed to determine porosity and thickness of a Fabry-Perot layer from the reflectivity spectrum using the Spectroscopic Liquid Infiltration Method (SLIM; see Adv. Funct. Mater. 2007, 17, 1153). User can choose either Bruggeman or Looyenga effective medium models. For porous sililcon samples, the Looyenga model is preferred. Either way, you need to provide an estimate of the refractive index of the material that comprises the skeleton of your porous material. Can feed a spectrum in from the clipboard or from a file. Can load from Ocean Optics (“OceanView”). It has some capability to load other .txt type files, and it can load any spectrum that you can put on the clipboard in the form of two columns (intensity in col 1; wavelength in col 2). (Aug 25, 2023)

An incomplete list of academic research groups working in the field of porous silicon and nano-scale silicon.

Prof. Vivechana Agarwal, Autonomous State University of Morelos; MEXICO
Prof. Ekaterina Astrova, Ioffe Research Institute, Saint Petersburg; RUSSIA
Dr. Bruno Azeredo, Arizona State University; USA
Prof. Hanna Bandarenka, Belarussian State University of Informatics and Radioelectronics; BELARUS
Prof. Giuseppe Barillaro, FoReLab, Università di Pisa; ITALY
Prof. Brahim Bessais, Res.& Tech. Centre of Energy; TUNISIA
Dr. Luca Boarino, INRIM, Torino; ITALY
Prof. Leigh Canham, University of Birmingham; UK
Prof. Andres Cantarero, University of Valencia, SPAIN
Dr. Ciro Chiappini, King’s College London; UK
Prof. Jeffrey Coffer, Texas Christian University; USA
Prof. Frederique Cunin, CNRS; FRANCE 
Prof. Saakshi Dhanekar, Indian Institute of Technology, Jodhpur; INDIA
Prof. Luca De Stefano, IMM, Naples; ITALY 
Prof. Thierry Djenizian, Universités d’Aix-Marseille; FRANCE
Prof. Laurent Francis, Université catholique de Louvain (UCLouvain); BELGIUM
Prof. Kazuhiro Fukami, Kyoto University; JAPAN
Prof. Gael Gautier, University of Tours; FRANCE
Prof. Justin Gooding, University of New South Wales, Sydney; AUSTRALIA
Mag. Dr. Petra Granitzer, University of Graz; AUSTRIA 
Prof. Dr. Patrik Huber, Hamburg University of Technology; GERMANY
Prof. Jinmyoung Joo, Ulsan National Institute of Science and Technology; SOUTH KOREA
Prof. Adrian Keating, University of Western Australia, Crawley; AUSTRALIA
Prof. Dokyoung Kim, Kyung Hee University; SOUTH KOREA
Prof. Kurt Kolasinski, West Chester University; USA
Prof. Roberto Koropecki, INTEC-UNL-CONICET, Santa Fe; ARGENTINA
Prof. Nobuyoshi Koshida, Tokyo University of A&T; JAPAN
Dr. Tushar Kumeria, University of New South Wales, Sydney; AUSTRALIA
Prof. Vesa-Pekka Lehto, University of Eastern Finland; FINLAND
Prof. Yang Yang Li, City University of Hong Kong; CHINA
Prof. Jan Macak, Czech Republic
Prof. Guido Mula, Università degli Studi di Cagliari; ITALY
Prof. Claudia Pacholski, Berliner Hochschule für Technik; GERMANY
Prof. Gabriela Palestino, Universidad de San Luis Potosi, SLP; MEXICO
Prof. Ji-Ho Park, KAIST; SOUTH KOREA
Prof. Kuiqing Peng, Beijing Normal University; CHINA
Prof. Enrique Quiroga, Benemerita Universidad Autonoma de Puebla; MEXICO
Prof. Klemens Rumpf, University of Graz; AUSTRIA
Prof. Amir Saar, The Hebrew University of Jerusalem; ISRAEL
Prof. Michael Sailor, University of California, San Diego; USA
Prof. Jarno Salonen, Turku University; FINLAND
Prof. Abel Santos, University of Adelaide; AUSTRALIA
Prof. Heldér Santos, University Medical Center Groningen; NETHERLANDS
Prof. Patrik Schmuki, Univerity of Erlangen; GERMANY
Prof. Ester Segal, Technion; ISRAEL
Prof. Honglae Sohn, Chosun University; SOUTH KOREA
Prof. Victor Timoshenko, Lomonosov Moscow State University, RUSSIA
Prof. Nico Voelcker, Mawson Institute, University of South Australia; AUSTRALIA
Prof. Ralf Wehrspohn, Fraunhofer Institute for Microstructure of Materials; GERMANY
Prof. Sharon Weiss; Vanderbilt University, Nashville; USA
Prof. Jianmin Wu, Zhejiang University; CHINA

An incomplete list of industry and government research groups working in the field of porous silicon and nano-scale silicon. (COI Disclosure: Prof. Sailor is a scientific founder (SF), member of the Board of Directors (BOD), Advisory Board (AB), Scientific Advisory Board (SAB), acts as a paid consultant (PC) or has an equity interest (EI) in the following: Aivocode, Inc (AB, EI); Bejing ITEC Technologies (SAB, PC); Hinalea Imaging (EI); Illumina (EI); Impilo Therapeutics (SAB, EI); Lisata Therapeutics (EI); Matrix Technologies (EI); Precis Therapeutics (SF, BOD, EI); Quanterix (EI); Spinnaker Biosciences, Inc. (SF, BOD, EI); TruTag Technologies (SAB, EI); and Well-Healthcare Technologies (SAB, PC). Although one or more of the grants that supported this research has been identified for conflict-of-interest management based on the overall scope of the project and its potential benefit to the companies listed, the research findings included in this publication may not necessarily relate to their interests.  The terms of these arrangements have been reviewed and approved by the University of California, San Diego in accordance with its conflict-of-interest policies)

2wiTech Commercial source of silicon nanoparticles, primarily focused on Li ion battery applications
Advanced Micromachining Tools (AMMT) Porous silicon etching equipment
Beijing ITEC Technologies Co., Ltd
Incize Porous Si used in RF circuits, complex characterization tools, and medical diagnostic devices based on porous Si
mapsi photonics Macroporous Si used in infrared optics
Matrix Industries Thermoelectric generators based on silicon nanotechnology
Oncosil Medical Treatment of pancreatic and liver cancer via radiotherapeutics embedded in porous Si
PicoTechnologies Nano Materials Co, Ltd. Sensors for explosives and industrial pollutants
Porous Silicon.com Porous silicon, etching equipment, specialized services
Precis Therapeutics Targeted therapeutics for infectious diseases
SiLiMiXT Porous silicon materials, specialized services
SiMPore Porous silicon films in silicon-based membranes for bio-MEMs applications: specimen and data capture
Sila Silicon nanoparticles embedded in carbon for Li ion battery applications
SiSaf Medical therapeutics, focused on RNAi
Spinnaker Biosciences Medical therapeutics with porous silicon
TruTag Technologies Taggants for anti-counterfeiting applications, specialized synthesis of porous silicon
Paraclete Energy A commercial source of silicon nanoparticles, primarily focused on Li ion battery applications.
Well-Healthcare Technologies Using porous Si in as an analytical platform for next-generation tumor liquid biopsies based on high-throughput mass spectroscopy (MALDI, SALDI, etc). Developing nanochips for rapid screening of microorganisms, cells, nucleic acids, antibiotics.

Upcoming national and international meetings of interest to the Porous Silicon community